Project Summary Rabbits are widely used for the study of human atherosclerosis. However, we note one major drawback of existing rabbit models. In almost all studies, rabbits at 4-12 months old are used for the induction of atherosclerosis. These rabbits are equivalent to human teenagers, who rarely suffer from atherosclerosis. On the other hand, aging is a major risk factor for cardiovascular diseases (CVD) including atherosclerosis. Telomerase, consisting of a reverse transcriptase protein (TERT) encoded by hTERT gene and a RNA subunit (TERC) encoded by hTERC, is the core enzyme that regulates human telomere lengths. Epidemic evidences accumulated in the past decade show that telomeres play important roles in CVD. In particular, short average leukocyte telomere lengths (LTLs) are correlated with increased incidence of CVD in people of different gender, race, age, disease condition, life style, and social status. Both Tert and Terc knockout (KO) mice have been generated. After 5-6 generations Terc KO (Terc -/-) mice displayed pre-mature aging phenotypes. However, double knockout of ApoE (a classic mouse model of atherosclerosis) and Terc (TERC-/- ApoE-/-) in mice led to less atherosclerosion1, which contradicted with the observations in humans where shorter telomere lengths correlated with increased incidence of atherosclerosis. In recent years we have established a robust platform to product KO and knock-in rabbits using CRISPR/Cas9 tools. In the present work, we propose to generate telomerase KO rabbits as an accelerated aging model for the study of atherosclerosis. In Aim 1, we will produce telomerase KO founder rabbits by CRISPR/Cas9 targeting telomerase reverse transcriptase Tert. Routine breeding will be employed to establish telomerase KO rabbit lines. In Aim 2, we will use the standard high fat high cholesterol (HFHC) diet protocols to induce atherosclerosis in G1 and G2 telomerase KO rabbits. In addition we are interested in if the percentage of vulnerable plagues positively correlates with the telomere shortening extent, and if spontaneous ruptures take place in accelerated aging rabbits. We expect that through the present work, a more real-life representative (i.e. aging) model will be developed for the study of atherosclerosis. This model is also useful for the study of other human diseases where aging is a risk factor.